The invention lies in the field of mobile battery booster technology, for example, for boosting automobile batteries. In particular, it deals with an apparatus capable of boosting such batteries through a cigarette lighter socket or directly, using a booster clip adapter. The invention may be generalized, however, to apply to any type of battery connection.
There exist, in the prior art, through-the-cigarette-lighter-socket boost charge systems; however, such prior art systems are incapable of starting the vehicle if the vehicle""s battery charge is below 6V. Six volts is barely enough to operate lights and to enable a clicking sound when the key is turned in the ignition, which is the sound of a starter solenoid trying to engage.
The prior-art techniques are many and varied. Some do not supply more than a nominal 12V DC to boost-charge a discharged battery through the lighter socket, instead relying on the mere difference of potential (between the charger and the battery) to slowly bring the discharged battery to a voltage high enough to operate the vehicle.
Some systems, like that disclosed in U.S. Pat. No. 5,637,978, use an inductive boost circuit powered by a lead-acid 12V battery and an electronically controlled semiconductor switch that grounds and un-grounds an inductor, so that back EMF aids the source voltage, resulting in a significantly higher voltage than the discharged battery, causing a charging current to flow. This technique, however, is slow and requires a large battery package to sustain the relatively inefficient boosting process.
Another technique, exemplified by the system of U.S. Pat. No. 5,883,491, uses boosting voltages significantly higher than the voltage of the target battery, using, for example, a 36V primary battery with an initially relatively low internal resistance, in comparison to that of a discharged vehicle battery. The initial current flow is relatively high but quickly decreases as the target battery""s voltage builds up and its internal resistance decreases. Note that as the booster""s battery discharges, its internal resistance increases, and heat is produced. After about five minutes of boosting, the user can start the vehicle. Such a booster may not, however, be used if the vehicle""s battery is so depleted that it is incapable of illuminating lights or activating a starter solenoid; that is, the voltage level should be in the range of 6-9V for a nominal 12V starting circuit (note that a 9-10V minimum voltage would be needed to actually start the vehicle, as opposed to the 6-9V voltage that is capable of [barely] activating a starter solenoid).
An object of the invention is to provide a through-the-cigarette-lighter-socket booster system that can rapidly boost-charge a discharged vehicle battery (the battery to be boosted will be referred to as the xe2x80x9ctarget batteryxe2x80x9d below) without causing the lighter socket fuse (typically, a 15 or 20 amp fuse) to blow.
Another object of the invention is to provide such a booster system that regulates current applied to the target battery so as to prevent damage to onboard electronic systems.
Another object of the invention is to provide such a booster system that is electrically efficient and, thus, able to utilize smaller, lighter batteries.
Yet another object of the invention is to provide such a booster system at a low cost.
The inventive apparatus addresses these and other objects, as well as the shortcomings of the prior-art systems described above. The battery booster system that contains current regulation circuitry so as to adjust for current as the target battery is recharging and the booster""s internal battery is discharging. Without such regulation, current surges may occur, which may cause the lighter socket fuse to blow. The booster system has a DC connection which may comprise a cigarette lighter plug for charging the target battery through a cigarette lighter socket and/or battery clips for directly charging the target battery at the terminals thereof.
In one embodiment, the inventive system uses electromechanical relays to switch between two voltage (equivalently, current) levels to control current. In another embodiment, pulse-width modulation-based techniques are used to control the current.
All embodiments are electrically efficient because they employ switching or interrupting techniques to control current, rather than heat-producing linear regulation techniques or inductive boost switching techniques. Furthermore, they are capable of boosting a depleted battery having a lower voltage than depleted battery voltages with which the prior-art through-the-cigarette-lighter-socket booster systems can be used.